[Qemu-devel] [PATCH v4 04/21] block: keep bs->total_sectors up to date even for growable block devices

[Paolo Bonzini <pbonzini@redhat.com>]

If a BlockDriverState is growable, after every write we need to
check if bs->total_sectors might have changed.  With this change,
bdrv_getlength does not need anymore a system call.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
        v4: use cache in bdrv_getlength
 block.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index 01b66d8..b11254a 100644
--- a/block.c
+++ b/block.c
@@ -2657,6 +2657,9 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
     if (bs->wr_highest_sector < sector_num + nb_sectors - 1) {
         bs->wr_highest_sector = sector_num + nb_sectors - 1;
     }
+    if (bs->growable && ret >= 0) {
+        bs->total_sectors = MAX(bs->total_sectors, sector_num + nb_sectors);
+    }
 
     tracked_request_end(&req);
 
@@ -2731,7 +2734,7 @@ int64_t bdrv_getlength(BlockDriverState *bs)
     if (!drv)
         return -ENOMEDIUM;
 
-    if (bs->growable || bdrv_dev_has_removable_media(bs)) {
+    if (bdrv_dev_has_removable_media(bs)) {
         if (drv->bdrv_getlength) {
             return drv->bdrv_getlength(bs);
         }
-- 
1.8.3.1